What's the different between show3D smooth and the segment's smooth?

I created a segment and show a well smooth 3D model with smooth factor=0.7. However, when I try to use the segment smooth(median,joint smoothing or closing) and the smooth factor=0 of show3D, the model seems very rough. I also tried the surface tool smooth(under smooth factor=0 of show3D), and the result still was very rough.
So, what’s the vtk smoother or the pipeline of the show3D?

Surface smoothing is required for reconstructing a continuous surface mesh from discrete samples stored in a labelmap volume. This smoothing does not remove any details from the segmentation. If you set surface smoothing to 0 then you will see the discrete samples instead of the reconstructed surface (each voxel of the labelmap will appear as a cube).

Smoothing effect is for removing irrelevant details (i.e., surface noise, speckled, small holes) from the segmentation.


Thank you very much!